1. Technical Field
The present invention relates to memory devices in general, and in particular to a read reference circuit for a sense amplifier within a chalcogenide memory device.
2. Description of Related Art
Phase transformation is a process of changing a phase change material from an amorphous state into a crystalline state or vice versa. Such phase transformation generally occurs when an electrical field is being applied to a phase change material. Because the amorphous state of the phase change material has a different electrical resistance from the crystalline state of the phase change material, the two different states can be utilized to represent a logical “0” and a logical “1,” respectively, for data storage applications.
An alloy known as chalcogenide, which includes germanium, antimony and tellurium, can be made to have phase transformation properties at a relatively low voltage. The electrical properties of chalcogenide are also particularly suitable for data storage applications. Since random access memories made of chalcogenide can easily be integrated with conventional logic circuits, chalcogenide random access memories have gradually become one of the more promising technologies for producing a new generation of memory devices, especially for light portable electronic devices.
Because of process variations of chalcogenide materials, the electrical characteristics of chalcogenide memory cells within a chalcogenide memory device tend to be less uniform than those of their complementary-metal oxide semiconductor (CMOS) counterparts. For example, the distribution of set and reset resistance values for chalcogenide memory cells may vary from one memory device to another. As a result, a static reference voltage that is commonly utilized by a sense amplifier circuit to determine a logical state of a memory cell within a CMOS random access memory device may not work properly for all chalcogenide memory cells within a chalcogenide memory device.